METHOD AND APPARATUS RELATING TO PUMPING OPTICAL FIBER

摘要

A method and apparatus for coupling substantial optical power into an optical fiber from the side without encumbering ends of the fiber. A special optical fiber, having a gain medium preferably including rare earth dopants in the core, is provided. One or more launch sections are selected at intervals along the special fiber with absorptive loops therebetween. The launch sections are stripped to their inner cladding layer (40), which preferably has a rectangular cross section, and positioned adjacent each other to form a launch region having a convex side mated to a launch port (44) shaped to conform thereto, and with a low refraction index material contacting the corresponding concave side of the launch region. The concave side is preferably supported by an upwardly convex support block. Pump light is directed by appropriate optics into one or more faces of a launch port, which has a refractive index substantially matching that of the inner cladding layer into which it transmits the pump light. The pump light entering each face is preferably provided by one or more stripe diodes about as long as the total width of the adjacent launch sections in the launch region, and may include combined light from a plurality of sources. As the pump light travels along the special fiber in the absorptive loops between the launch sections, it is significantly absorbed by the gain medium of the optical fiber and thereby contributes optical energy to generate or amplify light in the core. The launch port faces may reflect unabsorbed light back into the special fiber, even while transmitting pump light at a different wavelength into the launch port.